Impact of Amphiphilic Biomass-Dissolving Ionic Liquids on Biological Cells and Liposomes

Abstract

The toxicity of some promising biomass-dissolving amidinium-, imidazolium-, and phosphonium-based ionic liquids (ILs), toward two different cell lines, human corneal epithelial cells and Escherichia coli bacterial cells, was investigated. In addition, dynamic light scattering (DLS) and ζ potential measurements were used to study the effect of the ILs on the size and surface charge of some model liposomes. Capillary electrophoresis (CE) was used for determination of the electrophoretic mobilities of the liposomes and for determination of the critical micelle concentration (cmc) of the ILs. The toxicity of the phosphonium ILs was highly dependent on the longest linear chain of the IL, due to increasing hydrophobicity, with the long-chain phosphonium ILs being toxic while the shorter-chain versions were significantly less toxic or not toxic at all. Amidinium and imidazolium ILs showed no significant effect on the cells, within the concentration range used. Moreover, the more hydrophobic ILs were found to have a major effect on the surface charges and size distributions of the model liposomes, which can lead to disruption of the lipid bilayer. This indicates that the cytotoxicity is at least to some extent dependent on direct interactions between ILs and the biomembrane.

Effect of ionic liquids on the interaction between liposomes and common wastewater pollutants investigated by capillary electrophoresis

“…4. Adding [P 8444 ]Cl to the BGE diminished the interaction between the cationic compounds and the liposomes due to IL penetration into the liposome bilayer, which converts the surface charge of the liposomes to positive, as shown in our previous study [1]. The effect was most drastic for pindolol, metroprolol, and propranolol, which had the strongest interactions with the negatively charged liposomes.…”

“…On the other hand, ILs may even protect the membranes from interactions with compounds in polluted aqueous areas by changing the surface properties of biomembranes (e.g. surface charge) [1].…”

“…However, some phosphonium ILs are strongly hydrophobic due to their long alkyl chains, and may therefore have an even stronger impact on biomembranes. In our previous study we have shown that especially the long-chain phosphonium based ILs interact strongly with biomembranes and are, for example, significantly more toxic toward Escherichia coli and human corneal epithelial cell lines than short-chain ILs [1]. The toxicity of IL is at least affected by the alkyl chain length, lipophilicity, and the concentration of the IL [11].…”

Selected issues related to the toxicity of ionic liquids and deep eutectic solvents—a review

“…4. The toxicity of some promising biomass-dissolving amidinium-, imidazolium-and phosphonium-based ionic liquids, towards human corneal epithelial cells and Escherichia coli as well as on the size and surface charge of some model liposomes, were studied by Mikkola et al (2015). Despite the chain length, it was also proven that toxicity depends on hydrophobicity and surface charges and size distributions of model liposomes, which may disrupt the lipid bilayer.…”

Room-temperature ionic liquids meet bio-membranes: the state-of-the-art

“…Namely: (i) positive correlation between RTILs chain lengths, RTILs concentration, and cytotoxicity (Witos et al 2017;Losada-Pérez et al 2016;Dusa et al 2015;Galletti et al 2015;Galluzzi et al 2013;Kulacki and Lamberti 2008;Jeong et al 2012;Mikkola et al 2015;Jing et al 2016), (ii) shrinkage of the bilayer thickness (Lim et al 2014;Lim et al 2015) and (iii) variation of its elasticity (Dusa et al 2015) Fig. 9 Coarse-grained MD simulations of Ref.…”